アルミナ/ニオブ接合界面組織の高分解電顕観察と接合機構の考察

抄録

Atomic structure in the diffusion-bonded alumina/niobium was observed by high resolution electron microscopy. A minor impurity calcium was contained in the surface layer of niobium in the form of inclusion particles, which resulted in the formation of hibonite (CaO·6Al₂O₃) about 0.15 μm thick when the joining was performed without removing the surface layer. The hibonite layer served not only as warning to control the minor element but also as a useful marker of the original interface and allowed us to assess the amount of alumina back-precipitated from niobium during cooling of the joined specimen. The back-precipitation is consided responsible for the observed ordering in the structure of the bonded interface. It must be a useful mechanism to relax the thermal stresses which develop at the ceramic/metal interface during the cooling of the joined specimen.